Aidan Weston-Lewis, a member of RCEWA, said it was “a classic harbour scene by the greatest landscape painter of the 17th century”.

The painting shows Saint Paula leaving for Jerusalem. But Weston-Lewis said there was more to it: “For all its narrative interest and incidental detail, its real subject is light – the glorious, golden light of the sun rising over the sea which bathes the entire scene and imbues it with an extraordinary poetic beauty.”

The painting’s subject is an unusual one for a 17th-century artist, telling the story of Paula, a Roman matron of noble birth who underwent a spiritual conversion after the deaths of her husband and eldest daughter, renounced her worldly possessions and left Rome for Jerusalem in 385.

Vaizey said: “I hope that my placing a temporary export bar on this striking painting will allow time for a UK buyer to come forward and acquire it for the nation.

“It is of outstanding beauty and it would be tremendous to see it permanently on display in a UK gallery where it can be appreciated by all.”

It will cost more than £5m to keep the painting, A Mediterranean Port at Sunrise with the Embarkation of Saint Paula for Jerusalem, in the UK – money that British museums and galleries simply do not have.

Vaizey ordered the export bar to run until 1 May, which could then be extended until 1 November if a serious attempt is made to raise funds.